Abstract

The authors have studied the optical input interface for Nb single-flux-quantum (SFQ) circuits and demonstrated its operation using photomixing technique. Two tunable lasers of C band were used for photomixing. We adopted a multistage toggle flip-flop (TFF) circuit as the main part of the test circuit. As the first trial, we used lasers with wavelength difference of at around , which corresponds to the laser beat frequency of . The output signals from the 13- and 14-stage TFFs were observed and it showed the input SFQ frequency of . Thus, the authors demonstrated the conversion of the optical signal to SFQ signal and succeeded in driving the SFQ circuit.